1. Field of the Invention
The present invention relates generally to silicon-containing substituted aromatic compounds. More particularly, the present invention relates to compounds comprising silicon atoms linked together by a hydrocarbon chain and further comprising phenyl groups substituted with a glycidyl group or an allylic group.
2. Description of the Background Art
Epoxy resins are widely used as adhesives, encapsulants, and coatings for a variety of applications. In particular, for application to structural and electronic devices, epoxy resins are useful since they provide mechanical protection, good substrate adhesion, thermal and oxidative stability, and moisture and solvent resistance. In addition, compliance is a highly desirable property for these resins since it allows the dissipation of stress that accompanies thermal and mechanical cycling of the encapsulant. Furthermore, enhanced toughness provides mechanical protection against fracture damage. However, state-of-the-art systems exhibiting such compliance generally possess poor thermal stabilities. Another important property is the repairability of the adhesive, coating, or encapsulant. As expected, a rigid system is generally more difficult to repair and replace than a ductile one.
One group of epoxy resins particularly useful for electronic applications consists of epoxysilicone compounds, which are compounds comprising silicon atoms joined together by oxygen linkages and further comprising terminal glycidyl groups. Such epoxysilicone compounds have been known for many years and are described, for example, in the publications by Bilow, Lawrence and Patterson, "Synthesis and Polymerization of 1,3-bis(2,3-epoxypropylphenyl)tetramethylsiloxanes and Related Compounds, Journal of Polymer Science, Volume 5, 1967, pages 2595 to 2615 and by Patterson and Bilow, "Polymers from Siloxane-Containing Epoxides," Journal of Polymer Science, Volume 7, 1969, pages 1099 to 1110. As described in these references, such epoxysiloxane compounds were prepared by reacting the Grignard reagent derivable from an allybromobenzene with a large excess of dichlorodimethylsilane. The resulting compound, chlorodimethyl(allyphenyl)silane, must be isolated from excess dichlorodimethylsilane by repeated distillation steps. Chlorodimethyl(allylphenyl)silane was then hydrolyzed to give 1,3-bis(allyphenyl)-1,1,3,3-tetramethyl-1,3-disiloxane. Epoxidation was effected either with 3-chloroperoxybenzoic acid or trifluoroperoxyacetic acid. However, such a procedure is not only tedious, but also yields a product contaminated by impurities produced by rearrangement or reversion in which --Si--O-- groups break away from the rest of the molecule and form macrocycles or higher linear chains. In addition, the corrosive trifluoroperoxyacetic acid was difficult and dangerous to prepare on a large scale, and the 3-chlorobenzoic acid side product generated in the epoxidation reaction was so soluble in the desired product that complete removal of this acid residue was impossible. Furthermore, such a process is not conducive to tailor making the length of the siloxane chain.
When epoxy resins are used in structural applications for outer space, such as for adhesives or coatings in satellite components, the resin must not only be able to withstand the temperature extremes encountered in space, for example -148.degree. F. (-100.degree. C.) to 212.degree. F. (100.degree. C.), for extended periods of time, such as several years, but also be able to withstand the higher temperatures (350.degree. F. or 177.degree. C.) encountered in rigorous space applications for shorter periods of time. In addition, the material must meet the National Aeronautics and Space Administration (NASA) outgassing requirements, i.e., &lt; 1% total mass loss, and .ltoreq. 0.10% collectible volatile condensable materials, to insure that the material does not release gaseous component substances which would undesirably accumulate on other spacecraft parts in the outer-space vacuum. Heretofor, ductile, processible epoxy resins meeting all these requirements have been unobtainable.
Thus, a need exists for an epoxy resin for electronic and structural space applications which is tough, thermally and oxidatively stable, repairable, resistant to moisture and solvents, and which possesses low outgassing characteristics. In addition, a need exists for the preparation of the .psi., .omega.-alkenyl compounds from which such epoxy resins, among others, may be formed. The next to the lowest homolog of the .psi., .omega.-alkenyl group is the allyl group from which the glycidyl group is derived.